ABSTRACT
Objective:To explore the value of quantitative susceptibility mapping (QSM) in evaluating renal injury in patients with early diabetic nephropathy (DN).Methods:From October 2019 to December 2020, 32 patients with early DN were prospectively enrolled in the Third Affiliated Hospital of Soochow University. According to the estimated glomerular filtration rate (eGFR), they were divided into three groups: DN1 (eGFR≥90 ml·min -1·1.73 m -2, 11 cases), DN2 (60-<90 ml·min -1·1.73 m -2, 11 cases) and DN3 (30-<60 ml·min -1·1.73 m -2, 10 cases). At the same time, 32 normal volunteers were recruited as the control group. Both kidneys were scanned by QSM to measure the susceptibility of renal cortex and medulla. Paired samples t-test was used to compare the differences of the susceptibility between left and right kidneys and between cortex and medulla. One-way analysis of variance was performed to compare the differences of corresponding susceptibility values among different groups, and LSD- t was used for the pairwise comparison. Pearson correlation test was performed between the susceptibility value of the medulla and eGFR. The ROC curve was used to analyze the diagnostic efficacy of QSM parameters in the diagnosis of DN and different degrees of severity of DN. Results:The susceptibility values of bilateral renal medulla in normal volunteers and patients with DN were lower than those of renal cortex (all P<0.001). There was no significant difference in the susceptibility value between left and right renal cortex (all P>0.05). There was significant difference in the susceptibility value between left and right medulla (all P<0.05). There was no significant difference in the susceptibility value of bilateral renal cortex among the control group and the DN1－DN3 groups (both P>0.05). The susceptibility values of left renal medulla in control group, DN1, DN2 and DN3 groups were (-4.46±1.16)×10 -2, (-5.96±0.97)×10 -2, (-7.97±1.25)×10 -2, (-9.58±1.45)×10 -2 ppm, of right renal medulla were (-3.70±0.65)×10 -2, (-5.06±1.28)×10 -2, (-7.33±1.46)×10 -2, (-9.09±2.22)×10 -2 ppm, respectively. The overall difference of the susceptibility value of bilateral renal medulla was statistically significant (both P<0.05), and there were significant differences between each two groups (all P<0.05). The linear positive correlation were found between the susceptibility values of renal medulla and the corresponding eGFR (left kidney r=0.732, P<0.001; right kidney r=0.684, P<0.001). The areas under the ROC curve (AUC) of left and right renal medulla susceptibility value in diagnosis of normal and DN were 0.931 and 0.943, of DN1 and DN (2 and 3) were 0.952 and 0.883, of DN (1 and 2) and DN3 were 0.888 and 0.831, respectively. Conclusion:The susceptibility value of QSM quantitative parameter has a certain value in the staging and differential diagnosis of early DN, among which the susceptibility value of renal medulla has higher diagnostic efficiency.